XMP opinions?

Has anyone used Adobe's XMP much, either just to play or to incorporate into
a production workflow? What do you like and not like about it? What tools
have you used with it? 
 
thanks,
 
Bob DuCharme   www.snee.com/bob <http://www.snee.com/bob>        <bob@  
snee.com> weblog on linking-related topics: 
http://www.oreillynet.com/pub/au/1191
<http://www.oreillynet.com/pub/au/1191>